Computational Statistics & Data Analysis 34 (2000) 121–137 www.elsevier.com/locate/csda Condence interval estimation of overlap: equal means case Madhuri S. Mulekar ∗ , Satya N. Mishra Department of Mathematics and Statistics, University of South Alabama, Mobile, AL 36688-0002, USA Received 1 September 1998; received in revised form 1 October 1999 Abstract The estimators of the commonly used measures of overlap are known to be biased by an amount which depends on the unknown overlap. In general it is dicult to calculate the precision or bias of most ecological measures because there is no exact formula for the variance of the statistic and the sampling distribution is unknown (Dixon, 1993. In: Scheiner, S.M., Gurevitch, J. (Eds.), Design and Analysis of Ecological Experiments. Chapman & Hall, New York, pp. 290 –318.) Two resampling techniques, namely, Jackknife and Bootstrap along with the Taylor series approximation and transformation method are considered for the construction of condence intervals. Three measures of overlap frequently used in quantitative ecology and considered in this study are Matusita’s measure , Morisita’s measure, , and Weitzman’s measure, . c  2000 Elsevier Science B.V. All rights reserved. Keywords: Overlap coecients; Bootstrap; Jackknife; Matusita’s measure; Morisita’s measure; Weitz- man’s measure 1. Introduction Dixon (1993) commented that it is easy to calculate the value of many eco- logical indices or measures, but it is often hard to estimate their accuracy. This paper addresses the problem of making inferences about Overlap coecients based on an independent bivariate data. Use of relatively simple and widely applicable computational techniques such as jackknife, bootstrap, transformation and Taylor se- ries approximation is discussed. Three measures of overlap , , and  for normal populations that are frequently used by ecologists are considered in this study. Some ∗ Corresponding author. 0167-9473/00/$ - see front matter c  2000 Elsevier Science B.V. All rights reserved. PII: S 0167-9473(99)00096-1